Recovery of a human or cargo carrying capsule-spacecraft at the termination of a flight, whether a planned or emergency termination, may be effected by the use of drag devices such as parachutes, or by jet or rocket propulsion. Recovery systems typically mass between 10% and 25% of the recovered weight, so it is always desirable to minimize recovery system weight in order to maximize the effective payload of the capsule-spacecraft.
In the case of planed termination of a flight there are issues of deployment reliability after possible long-term space storage, uncontrolled drift from winds at the landing area, and cost of parachutes, whether replacement for a following flight, or refurbishment for reuse.
Rocket or jet propulsion has the ability to more precisely reduce the terminal velocity of a capsule-spacecraft, and very precisely control landing orientation and location, but is potentially heavy and requires the storage and use of volatile propellants, which present hazard or risk of the life of any crew.
While a landing rocket or jet system would confer the advantage of being able to precisely recover a capsule-spacecraft without risk of landing damage from water immersion in the case of a water landing, or physical or shock damage in the case of a land landing, nevertheless the risk of a failure of the jet or rocket based landing system is always present.
The primary risk is failure of the rocket or jet propulsion to function properly. A principal concern is that for optimum efficiency in the use of propellant, braking via jet or rocket propulsion should be undertaken when the spacecraft capsule is less than approximately 10-20 seconds from impact with the ground. This means there is little time to employ any other escape provision.
The usual suggestion for a backup escape system is the addition of one or more parachutes. Parachute(s) may be quickly deployed by rocket extraction methods or by mortars, but still require a few seconds to inflate and provide their optimal design-point drag reduction properties, see NASA TN D-5619 which is incorporated herein by reference. A key problem in the addition of parachutes to a vertical landing rocket or jet propulsion braking capsule-spacecraft is the inescapable fact that the weight of the capsule-spacecraft must be incremented by the weight of the parachute system, even though the capsule-spacecraft already is carrying the weight of the rocket landing system. Since weight is always at a premium for space missions, the penalty for carrying two complete and separate recovery systems is a serious operational and commercial disadvantage. For example, using the parametric weight guidelines of 10-25% for recovery systems if the capsule-spacecraft masses 10,000 pounds, without parachutes as a backup, but including the weight of the propulsive landing system, the propulsive system mass might be as much as 2,500 pounds. If parachutes are added, and are as light as only 10% of the landed mass, the capsule-spacecraft mass will grow to 11,000 pounds (10,000 pounds plus 10%, the lowest reasonable estimate for parachute system mass). This in turn means the mass of the propulsive landing system must grow in proportion, or more practically, the mass of the rest of the capsule spacecraft (i.e., the available mass of payload) must be decremented.
The invention described herein reduces this otherwise inevitable mass penalty.